Polyamide (PA) is commonly known as nylon, and amide groups of the polyamide are polarized and can form a hydrogen bond, and hence polyamide has excellent mechanical properties, and is a type of engineering plastics with good shock resistance and relatively strong toughness. This material is characterized by: 1. high crystallinity, high surface hardness, high wear resistance, small friction coefficient, good self-lubricating and silencing properties; 2. good low temperature performance and heat resistance; 3. non-toxicity, odorlessness, non-putridness, being self-extinguishing, good weather resistance, but poor dyeability; 4. good chemical stability, good seawater resistance, good solvent resistance, good oil resistance, but poor acid resistance; 5. good electrical insulation, which, however, is susceptible to temperature; 6. great water absorbing capability, and its dimensional stability and electrical properties being susceptible to water.
Nylon 6 (PA6) and nylon 66 (PA66) are the main varieties of nylon. Nylon 6 also has good physical, mechanical properties, such as high tensile strength, excellent abrasion resistance, impact resistance, outstanding chemical resistance and oil resistance. Nylon 66 is a kind of uniform thermoplastic high molecular polymers with symmetrical molecular structure containing six methylene, having high strength, wear resistance, solvent resistance, good self-lubricating characteristic, wide usage temperature range and other advantages, and being one kind of the engineering plastics that are relatively widely used.
Since nylon has excellent performance, nylon is widely used in industrial manufacturing, such as automobiles, instruments and meters, machineries, textiles and so on. The material is mostly used as components and structural parts. However, its great water absorbing capability and poor dimensional stability limits it from wider usage. The water absorbing capability of nylon can be reduced by filling enhancement modifier, so as to ensure that nylon works in highly hot and humid conditions, and in the meanwhile to increase rigidity, to reduce the high temperature creep degeneration and shrinkage rate, and to improve the dimensional stability, the impact strength, the abrasion resistance and the flame resistance. Generally, the enhancement modifier is mainly glass fibers, and the amount of the added glass fibers has a relatively large impact on the mechanical properties (large impact, tensile, and bending strength) of the composite material.
As being well known, rollers need to be mounted on lifting platform vehicles as the existing airport transportation equipment. The rollers can push a container and a container board by a roller shaft to move back and forth, left and right, or rotate. A roller made of aluminum alloy or other metal alloy provided by the existing technology is not reasonable, because the same metal has large intersolubility, and is easy to adhere and thereby be worn. In addition, there are two different mechanisms for abrasion of aluminum alloy under different loads. Aluminum alloy worn under low load is referred as slight abrasion or oxidation abrasion. The surface of aluminum alloy forms a layer of dense oxide film, and the thickness of the oxide film is up to about 2 μm. The layer of the oxide film is ruptured and falling off under the action of friction forces, thereby producing some shredded shaped worn debris. Especially, the rollers are prone to skid during the raining days. Consequently, the freights being transported are out of control, and the freights need to be manually pushed to be adjusted to the right direction. Many accidents occur every year in which the workers are injured due to slipping and falling when pushing the freights. In addition, the existing rollers made of aluminum alloy are prone to wear the bottom board of the container and the container board, and to generate too much noise when friction occurs, thereby causing damages to human ears.